Abstract

Analysis of stomach contents, laboratory observations of feeding behavior, the anatomy of the digestive system, and present-day geographic distribution of brachiopods furnish evidence indicating that dissolved and colloidal organic nutrients are the primary foods of articulate brachiopods, with plankton accounting for only a minor portion. Articulate brachiopods are not as common in the marine environment as other filter feeders, but in polar and subpolar areas where organic nutrients occur in high concentrations, populations rival fossil deposits in the Paleozoic. It is felt that in geologic history brachiopods declined when the nutrient-rich areas disappeared, either because of major shifts in oceanic currents, drastic decrease of nutrients reaching the ocean, or change in chemical or physical composition of the nutrients.

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